Certain measuring devices are known, such as those found in sphygmomanometers (blood pressure cuffs) which include a pneumatic bulb which inflates a pressure chamber of an attached sleeve that is fitted over the arm or leg of a patient. A bellows assembly, responsive to changes in fluid pressure of the pneumatic bulb and the sleeve pressure chamber is positioned in a dial indicator housing. The pointer of the dial indicator is interconnected to the bellows assembly by a gage mechanism whereby inflation of the bellows causes a corresponding circumferential movement of the pointer.
Typically, these mechanisms are quite complex and intricate, and are akin in terms of their manufacture and precision to Swiss watches. For example, in one such mechanism, a pair of diaphragm springs are attached adjacent opposing ends of a spindle. A bottom end of the spindle is placed in contact with the inflatable bellows assembly and a twisted bronze band perpendicularly disposed at the top end of the spindle is connected thereto in parallel by a horizontally disposed bent spring part. As the spindle axially deflects due to the inflation of the bellows assembly, the bent spring part is caused to deflect causing the band to twist. The pointer which is attached to the bronze band is thereby caused to rotate relative to an adjacent dial indicating face.
These known mechanisms include a plurality of moving components, each having multiple bearing surfaces. Therefore, such assemblies must be manufactured with a considerable degree of tolerancing to minimize errors, thereby creating a similar level of expense in their manufacture.
In addition, any adjustments required after assembly of such mechanisms, such as to null out the pointer needle or adjust the sensitivity of the device, require substantial teardown or at least significant and undesired disassembly of the measuring device.